Estudo fisiológico de Saccharomyces cerevisiae CAT-1 em resting cell após cultivo em diferentes condições

Abstract

The use of microorganisms to obtain products and services is an ancient practice that has been used empirically since the beginning of the society. Studies on cell metabolism are of paramount importance for a better biochemical understanding and for the establishment of appropriate cultivation conditions for obtaining bioproducts of interest through “cell factories”. The aim of this work was to evaluate the physiology of resting cells of the yeast Saccharomyces cerevisiae CAT-1 after carbon and nitrogen pulses. M9 mineral medium with adaptations and a nitrogen source limitation were utilized to establish the resting cells state. Kinetic studies to substrate consumption and secondary metabolites production were performed in microcultures using a microplate reader and posteriorly were evaluated in HPLC chromatography. The use of a lower concentration of nitrogen source (0,25 mM de NH4Cl) allowed the establishment of the best resting condition (0.5 optical density curve) to carry out the pulses. After these, growth was restored at the sucrose 0,1% condition with increase of biomass reaching absorbance values of 0.764, however there was no increase in the ethanol production. A second limiting condition was observed in the treatment with the addition of the nitrogen source in the absence of the carbon source, which may have affected cell growth and even the mechanism of glycolysis. In addition to variations in substrate consumption and metabolite production, invertase activity was also measured during the resting period and after the pulses. Results indicated presence of enzymatic activity (2,11 U mL-1) at the exact moment of the sucrose addition in the medium, explaining the constitutive nature of the enzyme. Although the aim of this work had been reached, there is a necessity of additional studies to better understanding the metabolic behavior in response to these disturbance.